1. Field of the Invention
The present invention relates to a setting tool for driving fastening elements in a constructional component and including a piston guide having a hollow chamber, a setting piston axially displaceable in the hollow chamber of the piston guide, a bolt guide adjoining the piston guide in a setting direction of the setting tool, and a piston stop device for the setting piston and arranged at an end region of the hollow chamber adjacent to the bolt guide, with the piston stop device having a damping element supported against a stop, and a stop member for the setting piston and adjoining the damping element in a direction toward the hollow chamber of the piston guide, and with the damping element, the stop member, and the stop having respective surfaces arranged axially opposite each other.
2. Description of the Prior Art
Setting tools of the type described above can be driven with solid gaseous, fluid fuels or with compressed air. In combustion-engined setting tools, the setting piston is driven by combustion gases. With the setting piston, fastening elements, such as nails or bolts, can be driven in a constructional component.
German Publication DE 39 30 592 A1 discloses a setting tool in which a setting piston is displaceable in a piston guide displaceably arranged in a housing sleeve of the setting tool. In order to actuate the setting tool, the setting tool should be pressed against a constructional component so that the piston guide is displaced into the housing sleeve. In order to reduce the piston energy in case of a faulty setting or at an excessive energy, there is provided in the piston guide, in an end region adjacent to the piston guide, an elastic annular body that blocks the displacement of the setting piston.
The drawback of the setting tool of DE 39 30 592 A1 consists in that with an excessive wear of the elastic annular body which is not detected, essential and expensive components of the setting tool can be damaged. Further, the piston collar, which engages the annular body, should have as large diameter as possible to prevents a premature destruction of the elastic annular body. This increases the weight of the setting tool. Still further, the piston rebounds from the annular body after impacting it because of its elasticity. This, in particular at a high setting energy, can result in undesirable secondary impact applied by the piston.
German Patent DE 196 17 671 C1, from which the present invention proceeds, discloses a powder charge-operated bolt setting tool with a piston displaceable in a guide bore. The piston has a piston head and a piston stem, with the piston head having, in its region adjacent to the stem, a conical section. Opposite the conical section of the piston head, there is provided a conical receptacle at the mouth end of the guide into which the conical section can be displaced at a faulty setting or at a setting process with an excessive energy. A damping disc, which is provided behind the conical receptacle in the setting direction, damps the impact of the piston.
An extensive wear of the elastic damping disc, which takes place in a setting tool of DE 39 30 592 A1, which was discussed further above, is prevented in the setting tool of DE 196 17 671 C1. However, in the setting tool of DE 196 17 671 C1, bounce of the setting piston and, as a result, a secondary impact cannot be avoided.
U.S. Pat. No. 4,824,003 discloses a setting tool in which between the piston guide and the bolt guide, there are arranged, one after another, a first rigid ring and an elastic ring. In the elastic ring, there is arranged a further rigid ring that limits the stroke of the first more rigid ring. The first rigid ring has an opening tapering in the setting direction. The collar surface of the piston adjacent to the first rigid ring is also conical. The profiles of the conical piston surface and of the conical opening are complementary to each other.
A drawback of the setting tool of U.S. Pat. No. 4,824,003 is the same as that of DE 196 17 671 C1, namely, bouncing of the setting piston leads to secondary impacts.
Accordingly an object of the present invention is to provide a setting tool of a type discussed above in which the drawbacks of the known tools are eliminated.
Another object of the present invention is to provide a setting tool of the type discussed above in which the rebound speed of the setting piston is reduced to a minimum.